Process for communicating with trains in motion by a high frequency current and applications



July 2 8, 1936. c 'lx 2 ,049,154

P ESS COMMUNICATING W-I TRAINS, IN MOT A H FREQUENCY CURREN ND APPLIGATIO Filed May 4, 1934 INVENTOR HENRI CHIREIX,

AT TOR N EYS Patented July 28, l936 waist PR ES F R MUNI AT NG ITH. reams IN' MorrroN BY A" HIGH Fina;- QUnNo r CUB-RENT nn rrLroATroNs Henri Ghireix, Paris, France, assignor to Societe Francaise Radio-Elcctrique, a corporation of France Application May 4, 1934, Serial No. 723,810

' In France May 13; 19.337

l Claims. (01. 2 4d .8.)

The present invention relates to a method of communicating with trains when they are in V motion. The invention isapplicable in particular to the distribution of public notices, of music and 5 to the transmission of orders, signals, or the like.

The object of" theinvent'ion'is toeifect the transmission of these notices or the like from stationary positions and to receive them by means of loud-speakers in the carriages while they are in motion or at rest, by employing simplf apparatus taking up little space and requiring no appreciable upkeep. A further object is to eii'ect with the train communication which is not inter'f'ered with by electric fluctuations arising from the power lines, motors, switches, sparking at the trolleys, etc.

It is known that the installation of wireless receivers in trains meets with numerous difficulties of this nature. It is also known that with such installations almost complete fading occurs in tunnels or stations. For this latter reason, wireless installations cannot under any circumstances be employed in underground railway systems.

The present invention overcomes these difficulties by the use alongside the track of a special line transmitting a modulated carrier current. According to a preferred embodiment of the invention, this carrier current is of high frequency and the line is composed of a series of elements tuned to this frequency in order to offer a minimum impedance. This arrangement permits the line to be easily charged and sufficient energy to be obtained, by induction in a frame located on the carriage, to supply directly a loudspeaker by 35 imple rectification of the potential collected without intermediate amplification being necessary.

It will be appreciated that this process presents the double advantage of reducing to a minimum the apparatus which must be installed in the carriages and of permitting a transmission of greater power than the interferences which are caused by the electric equipment of the carriages, the adjacent transmission lines and the like.

ferring to the annexed figures and to the follow- The invention will be better understood by rerent, 2 is the ceiver.

The frequency employed may be selected from the same order of values as the normal frequen= cies employed in radio-telephony, for example .0. to 10.? c cl s p e ond \=3.0Q to 3,000 m i z lline Figure 3) is compensated for the selected frequency'by means'of condensers 0 arranged at" intervals along the length thereof. The distance d between these'condensers will be made'mu'ch less than thew'av'length. a will, f reigamp b 'made' equal to If Z is the self inductance of a section of line and w the frequency, the capacity 0 will be determined so as to fulfill the resonance condition w ZC=1. The impedance of the line will then be a minimum.

The frame which is carried on the railway carriage, will be arranged in such a manner that one of the larger sides thereof is as close as possible to the conductor. For reasons of convenience, the frame will preferably be given an elongated shape and furthermore it will be arranged horizontally or vertically. 1

Figure 4 shows a diagrammatic view of the receiver. The frame 2 is tuned to the frequency of the line by means of a condenser 4.

The modulated high frequency potential induced in this circuit will be sufficient to supply directly a loudspeaker I simply by detection and without intermediate amplification.

There is shown in Figure 4 a self inductance 5 with a central tapping and a double anode valve 6. It will of course be understood that this valve may be replaced in practice by a dry rectifier so that the receiver does not include a valve or any source of current.

The invention has been described assuming that the current to be tranmitted is a telephone current and that the receiver is to operate a loudspeaker. It will be understood that the same installation can be employed in the transmission of orders or of telegraphic signals to a carriage while it is in motion. It will be sufficient in this case to transmit the signals to the high frequency line and to replace the loudspeaker by any suitable indicating or registering apparatus.

What I claim and desire to secure by Letters Patent of the United States is:-

1. System of communication between a signal transmitter and a mobile receiver installed in receiving frame and 3 is the rea railway carriage running upon a railway track comprising in combination a communication line disposed along the railway track, means for feeding the said communication line with a modulated carrier current supplied by the transmitter, the communication line being composed of a series of elements tuned to the frequency of the carrier current, and a close inductive coupling between the communication line and the receiver, said receiver being provided upon said railway carriage with a rectifier immediately followed by a final signal output device in order to directly indicate a fully developed signal independently of any interposed amplifying means.

2. In a system of communication between a signal transmitter and a mobile loop receiver installed as part of the equipment of a railway carriage running upon a railway track and a communication line extending along said track, said loop feeding said receiver, the combination of means disposing the loop of said receiver in immediate proximity to said communication line, means for feeding a modulated high-frequency carrier wave to the communication line and means for tuning the loop and the communication line to said high-frequency carrier wave, said receiver being provided upon said railway carriage with a rectifier immediately followed by a final signal output device in order to directly indicate a fully developed signal independently of any interposed amplifying means,

8. In a system of communication between a signal transmitter and a mobile loop receiver installed as part of the equipment of a railway carriage running upon a railway track and a communication line extending along said track, said loop feeding said receiver, the combination of means disposing the loop of said receiver in immediate proximity to said communication line, means for feeding a modulated high-frequency carrier wave to the communication line and means for tuning the loop and the communication line to said high-frequency carrier wave comprising series condensers interposed in said line, said'receiver being provided upon said railway carriage with a rectifier immediately followed by a finalsignal output device in order to directly indicate a fully developed signal independently of any interposed amplifying means.

4. In a system of communication between a signal transmitter and a mobile loop receiver installed as part of the equipment of a railway carriage running upon a railway track and a communication line extending along said track, said 

